Definition of ultrafine particles and why it is important to measure them

Atmospheric aerosol particles cover a size range from few nanometers up to tenth of micrometers. While coarse particles larger than one micrometer are dominated by mineral dust, see salt and biological particles (like pollen, bacteria and spores) fine particles smaller than one micrometer are secondary material built from gases such as sulfates, nitrates and organic carbon or are originated from combustion processes such as elemental carbon (soot). The size range of ultrafine particles smaller than 0.1 micrometer is dominated by such soot particles, especially in urban areas. Furthermore, soot particles are believed to be dangerous since they carry toxic trace compounds such as heavy metals and polycyclic aromatic hydrocarbons (PAHs). The concentration of such particles is highly variable and shows a significant daily and weekly variation, especially close to traffic.

Presently, such ultrafine particles are therefore of major concern to public health. They can deposit deeply in the lung and may cause cardiovascular and respiratory diseases. Until today there exist no regulations by law for the determination of their concentration in the ambient air. The prescribed mass concentration limits for the particulate matter such as PM10 or PM2.5 are not suitable for ultrafine particles. Because of their small size they contribute only insignificantly to the PM10 or PM2.5 particle mass concentration. Hence, the particle number concentration (PN) seems to be a better indicator to define the exposure to ultrafine particles in ambient air. There is thus need for appropriate measuring instrumentation and their application in air quality monitoring networks. Existing number size distribution measurements of ultrafine particles in urban areas in Europe are rare and are mostly driven by research institutes.

In the five European cities of the UFIREC project partners we will therefore measure fractions of particles in the range of 10 to 500 nanometers.  Because quality assurance is also a critical point we will compare and calibrate all measuring instruments consistently within the scope of the project.

Estimated impact of UFP on human health

Epidemiological and toxicological studies suggest that UFP may cause adverse human health effects greater than or independent of the effects compared to the larger particles. As mentioned above, ultrafine particles may carry toxic trace compounds. These compounds may erode in the lung and are then transported through the lining of the lung into the bloodstream. Although not all ultrafine particles are per se toxic, there is evidence that they can still initiate oxidative stress in the lung. Oxidative stress is a process, which alters lung cell chemistry, causing inflammation and setting in motion a cascade of health problems. Ultrafine particle are also small enough to cross the lung membranes and reach the bloodstream. They can cause there immune responses such as thickening of the blood, which leads to an increased chance of heart attacks and strokes. They can also be transported to different organs such as liver or heart via the blood stream. Elderly people and people with pre-existing diseases such as heart diseases and diabetes are supposed to be at special risk.

However, information on health effects of ultrafine particles is still limited, especially on a geographic basis. This project will investigate the short-term effects of size-fractioned ultrafine particles on mortality and morbidity in Germany, the Czech Republic, Slovenia, and the Ukraine. Thereby, the project aims to improve the overall sensitivity of the environmental and health care authorities and policy of the targeted regions to the health effects of ultrafine particles.

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